advertisement
16 September 2016

Dropped food on the floor? '5-second rule' debunked

Food that has been dropped on the floor should rather not be eaten as germs can transfer almost instantly, according to a study.

0

Most people have invoked the "five-second rule" after dropping something tasty on the ground at least once or twice in their lives.

Instantaneous contamination

Is that food really safe to eat? Probably not, a new study says.

After putting the five-second rule to the test, researchers at Rutgers University in New Brunswick, New Jersey, found contamination with bacteria can occur in less than one second.

"The five-second rule is a significant oversimplification of what actually happens when bacteria transfer from a surface to food," said study lead researcher Donald Schaffner, a professor and extension specialist in food science.

Read: Germs lurk in office kitchens

"Bacteria can contaminate instantaneously," he said in a Rutgers news release.

The scientists dropped foods of different textures, such as watermelon, bread and gummy candy, on a variety of surfaces including ceramic tile, stainless steel, wood and carpeting.

Less than one second

The scientists then contaminated each of these surfaces with a salmonella-like bacteria known as Enterobacter aerogenes for various lengths of time. The surfaces were allowed to dry completely before each type of food was dropped.

The researchers evaluated the transfer of the bacteria from each surface to each food item after letting it sit for less than one second, five seconds, 30 seconds and 300 seconds. Overall, they assessed 128 different scenarios 20 times for a total of 2,560 measurements.

Read: The age of killer germs

Longer exposure to the "dirty" surfaces and moisture made the spread of germs worse. But the researchers found that contamination could occur in less than one second.

The wetter the food, the more bacteria got on it, the study found.

"Transfer of bacteria from surfaces to food appears to be affected most by moisture," Schaffner said.

'Topography' plays a role

"Bacteria don't have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food," he said.

Read: Hand-held torch zaps germs

Watermelon was most contaminated after being dropped. Gummy candy had the least amount of bacteria, suggesting germs more easily transfer to wet or moist foods, the study authors said.

The researchers also found foods dropped on the carpet sample had less contamination than those dropped on tile and stainless steel. The food items dropped on wood had more variable levels of contamination, the researchers noted.

"The topography of the surface and food seem to play an important role in bacterial transfer," Schaffner said.

The study was published recently in Applied and Environmental Microbiology.

Read more:

Germs lurk in unexpected places

A kiss transfers 80 million germs

Could gut germs underlie Western allergies?

 
NEXT ON HEALTH24X
advertisement

Live healthier

Don't even bother »

SEE: When you cough, this is what happens to your body LISTEN: Can you spot the smoker’s cough?

7 cough remedies that definitely don’t work

A chronic cough can be the bane of your life. Here are seven cough remedies you shouldn't waste your time with.

Be in the know! »

How to manage sensitive teeth 5 ways runners mess up their teeth

Oral health basics: what you need to know

Dr Simon Reeves talks us through the importance of oral health basics. Here’s how to care for your teeth properly.